ALMA has observed the assembly of some the universe's earliest galaxies for the first time in history.
A few hundred million years after the Big Bang the universe was full of hydrogen gas, until it was cleared away by the formation of large objects such as stars and black holes, the European Southern Observatory reported. This phenomenon is referred to as the epoch of reionization, but little is known about these first galaxies. A team of researchers looked at the galaxy BDF 3299, and picked up a clear signal of glowing carbon coming from the galaxy's side.
"This is the most distant detection ever of this kind of emission from a 'normal' galaxy, seen less than one billion years after the Big Bang. It gives us the opportunity to watch the build-up of the first galaxies. For the first time we are seeing early galaxies not merely as tiny blobs, but as objects with internal structure!" Said co-author Andrea Ferrara of the Scuola Normale Superiore in Pisa, Italy.
The researchers believe the off-center appearance of the gas is due to central clouds that are being disrupted by the harsh environment created by the newly formed stars. The team combined ALMA observations with computer simulations to gain insight into processes occurring within the earliest galaxies. The scientists are now able to calculate the "escape of ionizing radiation and the complex structure of the interstellar medium," and compare them with other observations. The findings suggest BDF 3299 was partially responsible for reionization.
"We have been trying to understand the interstellar medium and the formation of the reionization sources for many years. Finally to be able to test predictions and hypotheses on real data from ALMA is an exciting moment and opens up a new set of questions. This type of observation will clarify many of the thorny problems we have with the formation of the first stars and galaxies in the Universe," said Andrea Ferrara.
